Cure characterization of carbon fiber reinforced phenyl-ethynyl terminated oligoamic acid by FTIR–photoacoustic spectroscopy

Curing of phenyl-ethynyl terminated oligoamic acid resin reinforced with carbon fiber and of the neat extracted resin was investigated by FTIR–photoacoustic spectroscopy (PAS). Imidized oligoamic acid with phenylethynyl termination form the precursor for the formation of phenyl-ethynyl terminated imide (PETI), which are employed for high temperature, high performance applications. The reaction kinetics was modeled based on two-stage, first order kinetic model for the imidization process, whereas the crosslinking was modeled on a simple first order model. Our results show that the imidization is kinetically controlled, whereas the crosslinking stage exhibits kinetic and diffusion controlled phases. The activation energy for the PETI composite and resin crosslinking was calculated to be 22.6 and 23.2 kcal/mol, respectively. Variation in rates for resin and composite are discussed. The cure extent as determined by isothermal DSC and by FTIR–PAS measurements were found to be in good agreement.